Stunning effects after a diagnostic dose of iodine-131.
OBJECTIVE
To understand stunning effects of a diagnostic dose of iodine-131 (I-131).


METHODS
Four hundred and sixty-eight patients (101 males, 367 females, ages: 6-75 years with well differentiated thyroid cancer, following total or nearly total thyroidectomy, were studied. One hundred and eleven MBq (3 mCi) diagnostic (Dx) doses of I-131 whole body scan (WBS) were obtained after withholding thyroxine after 6 weeks and triiodothyronine for 2 weeks. One week to one month later, 3.7-7.4 GBq (100-200 mCi) I-131 was given to them, then a therapeutic (Tx) dose of I-131 WBS was performed. The serum thyroid simulating hormone level was usually above muIU/ml.


RESULTS
Of the 468 patients, 344 (73.5%) had scintigraphic patterns of apparently decrease uptake in 240 thyroid remnants and 104 metastatic lesions on the Tx dose of I-131 WBS compared to Dx dose of I-131 WBS. Stunning phenomenon occurred in 50 cases, including 42 thyroid remnants and 18 metastatic lesions.


CONCLUSIONS
Dx dose of I-131 may influence the uptake of a subsequently administered Tx dose of I-131.
Kao
C H
CH
Department of Nuclear Medicine, Taichung Veterans General Hospital, Taiwan, Republic of China. kao@vghtc.vghtc.gov.tw
Yen
T C
TC
D018263:Adenocarcinoma, Follicular / Q000000981:diagnostic imaging / Q000532:radiotherapy; D000293:Adolescent; D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging / Q000532:radiotherapy; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D013997:Time Factors; D014055:Tomography, Emission-Computed
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals